The invention relates to an x-ray primary radiation diaphragm assembly comprising two pairs of diaphragm plates staggered 90.degree. which, when said diaphragm is mounted in operative relation to an x-ray tube housing, are disposed close-to-focus, and comprising two pairs of diaphragm plates, likewise staggered 90.degree., which, when said diaphragm is mounted, are disposed remote-from-focus, and wherein the plates of each pair of diaphragm plates are commonly adjustable symmetrically relative to the longitudinal axis of the diaphragm assembly such that the diaphragmed beam path configuration has the shape of a pyramid with its vertex lying at the focus of the x-ray tube (when said diaphragm assembly is mounted in operative relation to an x-ray tube housing).
A primary radiation diaphragm assembly such as this enables the beam of rays of the x-ray tube to be shaped to any optional image format. A so-called double-slot diaphragm has become known for this purpose, manifesting two pairs of plates which are adjustable in virtually one plane in mutually perpendicular directions, whereby the two plates of each pair are adjustable by means of an endless cable guided over cable pulleys disposed in mutual coaxial relation. Due to the finite extension of the focal point of the x-ray tube, a double slot diaphragm assembly such as this has the disadvantage that a penumbral region results about the actual shadow image which can be troublesome in certain instances.
With the aim of possibly avoiding this penumbra region, a so-called multi-depth diaphragm has been produced, such as is essentially the subject of the present invention, wherein a plurality of diaphragm planes are arranged in parallel and spaced apart from one another, and wherein the plates in the diaphragm planes are commonly adjustable in proportion to one another. As a consequence of the greater distance of the foremost diaphragm plane from the tube focal point (and thus a greater proximity to the patient), a shadow image is obtained having a considerably greater marginal definition. However, these multi-depth diaphragms have a rather complicated construction, and their manufacture therefore involves considerable outlay and expense.
A multi-depth diaphragm such as this is known which is assembled in building-block fashion from double-slot diaphragms adjustable by means of cable lines. The double slot diaphragms are coupled to one another by means of a suitable transmission gearing proportioned to the different distances of the diaphragm planes from the tube focal point. The disadvantage of this known x-ray primary ray diaphragm lies in its complicated construction, and, in addition, on account of the cable gearing, in its susceptibility to failure.